A vehicle engine control unit disclosed in Patent Literature 1 includes an electric oil pump in addition to an oil pump provided for a drive line to supply a controlling hydraulic pressure to a power transmission system such as a continuously variable transmission. In this engine control unit, the electric oil pump is stopped after an engine stop control operation is executed. Because of this, even when the oil pump is stopped as a result of the engine being stopped, working fluid is supplied to the power transmission system by means of the operation of the electric oil pump. As a result, the occurrence of a function failure in the power transmission system can be prevented which would otherwise occur when the engine is stopped, thereby making it possible to prevent the occurrence of a power transmission failure when the vehicle is started again.
The engine control unit executes an idling stop control routine shown in FIG. 12. In the idling stop control routine, as shown in FIG. 12, in step s1, vehicle's operating information (data) is inputted from respective sensors and is then stored. In s2, it is determined whether or not the engine is running where an engine revolution speed Ne exceeds a predetermined value Ne1 which is a start determination value. If it is determined that the engine is running, the routine proceeds to step s3, whereas if it is determined that the engine is stopped, the routine proceeds to step s4. When the routine reaches step s4 as a result of the engine being stopped, it is determined whether or not a key-on signal or start signals Ss, Sk have been inputted as a result of an engine starting condition being met. If No, the routine returns to the main routine.
When the routine proceeds to step s3 as a result of it being determined that the engine is running in step s2, an engine stop permissive vehicle speed setting operation is executed. In the engine stop permissive vehicle speed setting operation, a subtracted value δV is obtained from the current vehicle speed Vcn and a vehicle speed Vcn-1 which resulted a certain length of time ago, deceleration−α=δV/δt is calculated, and an engine stop permissive vehicle speed Vo corresponding to the deceleration−α is operated by use of a permissive vehicle speed setting map mp1. Then, the routine proceeds to step s6.
In step s6, the engine stop control operation is executed. As shown in FIG. 13, in the engine stop control operation routine, in step b1, it is determined whether or not the deceleration−α is equal to or smaller than a stop enablement determination value −α1. If Yes, and when it is considered that the deceleration−α stays within a braking mode which does not make the driver or an occupant feel a sensation of physical disorder that he or she normally feels, the routine proceeds to step b2. In step b2, it is determined whether or not the current vehicle speed Vcn is equal to or smaller than the engine stop permissive vehicle speed Vo. If Yes and when it is determined that the vehicle speed stays within a braking mode which can permit an automatic stop control, the routine proceeds to step b3. On the contrary, if it is determined that the vehicle speed is in a driving region where the automatic stop control is to be canceled, the routine returns to the main routine with doing nothing.
In step b3, it is determined whether or not a brake pedal is being depressed (a depression signal Sb ON). If it is determined as ON, the routine proceeds to step b4, whereas if OFF, the automatic stop condition is not satisfied, and the routine returns to the main routine with do nothing. In step b4, as a result of the automatic stop condition being established, a fuel supply system and an ignition system are stopped, and even in the event that the vehicle speed Vc is not zero, an engine stop is executed, the routing returning to the idling stop control routine.
After step s6, the routine proceeds to step s7. In step s7, the electric oil pump is driven which supplies a controlling hydraulic pressure to the power transmission system such as a continuously variable transmission, and the routine returns to the main routine. This operation drives the electric oil pump to enable the working hydraulic pressure to be supplied to a hydraulic pressure switching mechanism when the engine is stopped even in the event that the oil pump of the drive line is stopped as a result of the engine being stopped.